Drawing presses



Dec. 22, 1970 J. ROPERTZ DRAWING PRESSES Filed Nov. 19, 1968 IN V EN TOR.

JOHANN ROPERTZ United States Patent 3,548,626 DRAWING PRESSES Johann Ropertz, Dusseldorf, Germany, assignor to Schloemann Aktiengesellschaft, Dusseldorf, Germany, a German company Filed Nov. 19, 1968, Ser. No. 776,901 Claims priority, application Germany, Dec. 9, 1967, 1,652,939 Int. Cl. B21d 45/00 US. Cl. 72-344 4 Claims ABSTRACT OF THE DISCLOSURE A drawing press for the production of thick-walled hollow bodies, wherein the initial workpiece is provided with a blind hole, whereby it is slipped on to a stationary mandrel, and is drawn out, upon the mandrel, into a thick-walled hollow body by means of dies or drawing bands which are pressed over the workpiece by a crossbar or the like, which is moved parallel to the longitudinal axis of the mandrel and back again into its initial position by way of tension rods, characterised by the provision of a withdrawing device preferably engaging in recesses in the tension rods, which acts upon the closed end of the hollow body. The withdrawing device may advantageously be provided with automatically engaging and automatically releasable clamping jaws.

This invention relates to a drawing or drop-forge press, for the production of thick-walled hollow bodies, wherein the initial material is provided with a blind hole, and with this blind hole is slipped over a stationary mandrel, and by means of dies, which are pressed by a crossbar or the like, moving parallel tothe longitudinal axis of the mandrel, and movable back over the initial material into the initial position from time to time by way of pull rods, is drawn out upon the mandrel to a thickwalled hollow body.

For the production of thick-walled hollow bodies by Erhardts process, a billet, usually a hexagonal billet, is initially pierced in a punching press, that is to say, provided with a blind hole, the internal diameter of which corresponds to that of the desired hollow body. This initially punched billet, the so-called pierced piece, is then drawn out, as initial material, in a drawing press, over a mandrel, to the desired external form of the hollow body.

Usually the finished workpiece is stripped off the mandrel with a fork. 'In that case the fork forces its way 0 into the workpiece, and occasions permanent deformations at the open end of the hollow body, and these deformations, on account of the corresponding dimensions of a cover for instance, for closing the hollow body, are very objectionable, and therefore have to be removed. It is therefore the object of the present invention, when effecting the drawing in a drawing press of the kind hereinbefore mentioned, to avoid any deformation of the open end of the hollow body.

According to the invention it is proposed to couple a withdrawing device, acting on the hollow body at its closed end, to the tension rods of the drawing press. The closed end of the hollow body is here particularly suitable, in consequence of its intrinsic rigidity, as the point of application of the withdrawing device. Moreover any deformation of the bottom or inner end or of the outer wall of the hollow body, arising from the withdrawal, is unimportant since the bottom of the hollow body will be cut off if the hollow body is to be employed as a tube, and the thickness of the bottom of the hollow body is so great that its deformation, if the hollow body 3,548,626 Patented Dec. 22, 1970 is to be used as a pressure vessel or as a hydraulic cylinder for instance, does not impair the operation or the safety of the hydraulic cylinder or pressure vessel.

The hollow body, during the withdrawal, may advantageously be stressed in tension instead of pressure, so that the withdrawing force acting upon the hollow body can be increased as compared with the stripping force of a fork, since the maximum permissible loading of the hollow body in tension is greater than that in compression, and therefore the conical taper of the mandrel, which does indeed facilitate the stripping or withdrawing from the mandrel but is otherwise disadvantageous for the hollow body, may be reduced.

In the tension rods of drawing presses of the kind here inbefore set forth, recesses are usually provided for the accommodation of a pressure plate, with which the socalled pierced piece is slipped on to the mandrel. Such recesses also serve, according to the invention, for conmeeting or coupling the withdrawing device to the tension rods, in that the withdrawing device is simply engaged in these recesses. According to the invention the withdrawing device, before the last drawing operation, is already placed in the recesses of the tension rods, and spaced away from the die by a definite distance which corresponds to the total length of the finished hollow body. With the last drawing operation the die then travels so far beyond the work-piece that the withdrawing device is located over the bottom of the drawn hollow body, so that the succeeding rearward movement of the die can be used for the withdrawal of the hollow body from the mandrel. In this way there is advantageously a saving of time, as compared with the drawing operation in known drawing presses, since, in these known drawing presses, before the stripping of the hollow body from the mandrel, it is usually first of all necessary to bring along the fork, with a crane and with the help of an operator, and connect the fork with the tension rods. In the withdrawing device according to the invention, clamping jaws are preferably provided, which automatically clamp the hollow body during the rearward move ment of the die and the return travel of the drawing press, and which, after the withdrawal of the hollow body, that is to say, when there is no longer any frictional force acting upon the clamping jaws between the mandrel and the hollow body, can easily be swung apart for the releasing of the hollow body from the withdrawing device. After the hollow body has been released from the withdrawing device, it is carried away upon the roller bed, which likewise serves for bringing in the socalled pierced piece.

The invention will now be more fully described with reference to an embodiment illustrated by way of example in the accompanying drawings in which:

FIG. 1 is a plan view of a drawing press, with a finishdrawn hollow body, and a withdrawing device put in;

FIG. 2 is a plan view of the withdrawing device according to the invention on a larger scale: and

FIG. 3 is an end view of the withdrawing device of FIG. 2.

In FIGS. 1 to 3 is shown a drawing press with a stationary mandrel 1, upon which the original material, in this case the so-called pierced pieces, hereinafter referred to as workpieces 4, are drawn out into hollow bodies. This is effected by means of dies, so-called drawing bands 22 to 28, which are pressed individually over the workpiece 4 by a crossbar 8 moved by power pistons. For this purpose the crossbar 8, after each working stroke or drawing operation, is moved back by retracting cylinders 7 by way of tension rods 14 into its initial position, and the drawing band pertaining to the next working stroke is brought in by a crane between the crossbar 8 and the mandrel 1, so that the drawing band, in a subsequent forward movement of the crossbar 8, is pressed over the workpiece 4. In FIG. 1 the workpiece 4 is drawn out to a desired final dimension, that is to say, all the drawing bands 22 to 28 have been pressed over the workpiece 4 by the crossbar 8, while simultaneously with the last drawing operation and with the drawing band 28, a withdrawing device 32, which had previously been placed in corresponding recesses 15 in the tension rods 14, has been moved over the closed end or bottom of the workpiece 4.

The withdrawing device 32 carries, as illustrated in FIGS. 2 and 3, two clamping jaws 33, rockable about bolts 34, in which the bottom of the workpiece 4, during the return travel of the drawing press and the retraction of the crossbar 8 and of the withdrawing device 32, is automatically gripped or clamped, so that the workpiece 4, during the further rearward travel of the drawing press, is pulled off the mandrel 1.

As the drawing press is reaching its initial position, the drawing device, with its clamping jaws 33, travels towards stationarily arranged pins 35, whereby the clamping jaws 33 are swung away from one another and the workpiece 4 is released from the withdrawing device 32, and is received for removal by a roller table 17 arranged underneath the drawing press.

The drawing head of an ordinary commercial draw bench may be used as a withdrawing device.

I claim:

1. A drawing press for the production of thickwalled hollow bodies from workpieces provided with a blind hole, comprising: a stationary mandrel on to which the workpiece is slipped by its blind hole, a plurality of dies adapted to be passed over the workpiece in succession so as to reduce its external diameter progressively, a crossbar adapted to be moved to and fro parallel to the longitudinal axis of the mandrel and to engage the dies one at a time and impel them over the workpiece, tension rods for reciprocating the crossbar, power units for reciprocating the tension rods, and a withdrawing device adapted to act upon the closed end of the hollow body so as to draw it off the mandrel.

2. A drawing press as claimed in claim 1, the tension rods being formed with a series of recesses, and the withdrawing device being adapted to engage in the said recesses so as to be reciprocated by the tension rods.

3. A drawing press as claimed in claim 2, the tension rods being of such length, relatively to the workpiece, that after the last die has operated upon the workpiece, the space between the die and the withdrawing device is greater than the total length of the finished hollow body, so that the subsequent return movement of the die can be used for the withdrawal of the hollow body from the mandrel.

4. A drawing device as claimed in claim 3, the withdrawing device further comprising automatically engageable and automatically releasable clamping jaws for gripping the closed end of the finished hollow body.

References Cited UNITED STATES PATENTS 1,936,790 11/1933 Heetkamp 72-344 2,024,186 12/1935 Rober 72-349 2,341,667 2/1944 Stacy 72-344 RICHARD J. HERBST, Primary Examiner 

